Now it correctly has -1 after initialization.

The elements z-index is no longer ignored.
Isolation helps for having negative z-indices. Those elements no longer 
are hidden behind parent elements.
The helper grid need to have a large negative z-index to not interfere.

#657

#656

#651

#635

Fieldsets have a browser-style of "min-width: min-content". This 
inverses the usual sizing where children adhere to the parent size, 
which is not wanted here or anywhere else. To prevent running into this 
hard to find problem again, it changed globally.

Move element specific components to sub folder and just generally 
improve the file/component structure.

Droplist label is not shown anywhere but sadly part of the model.

Use textareas in several places where longer text is expected/common.

#637

as this causes images to be displayed too small on iPads
when they are first loaded.

This is necessary now because mouseenter events are only handled when 
not already being over a list.

Mouuseenter, mouseleave for list and items are now always active and no 
longer added after the drag has started (they check of a drag operation 
is going on though). This makes the code simpler and more managable.

This reverts commit 8da0e95c.

As the registration of hidden and visible pages can take place
asynchronously, the array of hidden and visible pages must be sorted

Add edit button, so it is clear where to click to edit.

Restrict maximun size of image.

#638